Protective garments for wear in rain and other wet conditions should keep the wearer dry by preventing the leakage of water into the garment and by allowing perspiration to evaporate from the wearer to the atmosphere. “Breathable” materials that do permit evaporation of perspiration have tended to wet through from the rain, and they are not truly waterproof. Oilskins, polyurethane coated fabrics, polyvinyl chloride films and other materials are waterproof but do not allow satisfactory evaporation of perspiration.
Fabrics treated with silicone, fluorocarbon, and other water repellants usually allow evaporation of perspiration but are only marginally waterproof; they allow water to leak through under very low pressures and usually leak spontaneously when rubbed or mechanically flexed. Rain garments must withstand the impingement pressure of falling and wind blown rain and the pressures that are generated in folds and creases in the garment.
It is widely recognized that garments must be “breathable” to be comfortable. Two factors that contribute to the level of comfort of a garment include the amount of air that does or does not pass through a garment as well as the amount of perspiration transmitted from inside to outside so that the undergarments do not become wet and so that the natural evaporative cooling effect can be achieved. However even recent developments in breathable fabric articles using microporous films tend to limit moisture vapor transmission if air permeability is to be controlled.
Many waterproof structures currently available comprise a multilayer fabric structure that employs the use of a hydrophobic coating. This fabric structure is typically made of a woven fabric layer, a membrane-type microporous layer, and another woven layer. The microporous layer is the functional layer of the construction that provides the appropriate air permeability and moisture vapor transmission rate necessary for the targeted application. For examples of such structures see U.S. Pat. Nos. 5,217,782; 4,535,008; 4,560,611, and 5,204,156.
The material currently in use in many waterproof and/or windproof breathable garments is an expanded PTFE (e-PTFE) microporous structure that is white in color. This material cannot be dyed and therefore produces a white edge when cut and sewn into a garment. This white edge is not acceptable in the higher-end market applications to which this microporous structure is targeted. Post-processing steps to hide the white edge must be included in the final construction of any fabric structure containing the e-PTFE.
What is needed is a microporous layer that can be dyed to match the color of the other layers in the fabric structure. This coloring can be done either during or after the production of the submicron nonwoven structure. This coloring of the microporous layer will omit any post-processing step that is done to hide a white edge.
What is also needed is a microporous layer that can be thermally bonded in order to eliminate the stitching in a fabric structure. This thermal bonding will create a completely seam-free waterproof and/or windproof structure and will eliminate any post-processing that must be done at the site of a seam in order to regain the waterproof and/or windproof functionality of a fabric structure.
While it is well known for example that e-PTFE is a desirable material for use in waterproof breathable and wind barrier fabrics in garments, the high temperature melting point and other negative aspects of e-PTFE mean that it does not readily melt at the same temperature as common textile materials such as nylon or polyester. In garments it is increasingly desirable to seam seal by thermal or ultrasonic welding techniques.
These techniques depend on the melting temperature of the materials involved. Lower melting temperatures are more amenable to these techniques. In addition, similar melting characteristics of multicomponent structures are more desirable so that the materials combine more properly within the weld.
The present invention is directed towards a layered material for a garment that provides controlled liquid water resistance in the presence of high vapor transmittance and is hence highly waterproof and is also dyeable and weldable.